1. Field of the Invention
The invention relates to a method for producing organically-modified oxide, oxinitride or nitride layers on large areas through vacuum coating. Preferred applications of these layers are transparent barrier films for packaging materials and transparent corrosion-protective or anti-abrasion layers for window faces, mirrors, decorative surfaces, or facade coatings.
2. Discussion of Background
It is known to produce layers for these applications by varnishing with transparent varnish layers or laminating transparent plastic films. Although an adequate barrier or corrosion-protective effect can be obtained in many cases, the abrasion resistance is very low, and weather- and UV-resistance prove to be insufficient in outdoor applications.
Much higher abrasion resistances and good barrier or corrosion-protective properties can be attained with a much lower material expenditure by the application of transparent oxide layers in a vacuum. Coating takes place by vapor-deposition, sputtering, or plasma CVD techniques (G. Kienel: "Vakuumbeschichtung [Vacuum Coating]",Vol. 5, VDI-Verlag, Duisseldorf, 1993). However, inorganic oxide layers produced in this way have a much lower flexibility compared to organic layers produced by varnishing or laminating. This substantially impairs the initially very good properties of the vacuum-deposited oxide layers during use and further processing of the coated films, sheet metals, or plates. Particularly, subsequent stretching or deep-drawing of the coated materials is hardly possible.
It has already been attempted to combine the high flexibility of organic coatings with the high abrasion and weather resistance of the oxide layers. Cited as an example are the so-called called "organically-modified ceramic layers" ("ORMOCER" layers), which are produced according to the Sol-Gel process and are to be applied similarly to varnish layers (R. Kasemann, H. Schmidt: New Journal of Chemistry, Vol. 18, 1994, No. 10, Page 1117). However, they require a layer thickness similar to those of customary varnish layers. Furthermore, although their resistance to abrasion and weather is better than that of varnish layers, it is not as good as that of thin vacuum-deposited oxide layers.
Moreover, it is a known method to produce organic layers with an inorganic oxide component in a way that the organic layers are deposited by plasma polymerization in a vacuum, using organometallic or organosilicon vapors as monomers for the plasma polymerization, so that a concurrent oxygen admission results in the formation of both metallic oxide and silicon oxide molecules that will be incorporated into the growing organopolymeric layer (JP 2/99933). Depending on both the monomers and the proportion of oxygen used, the oxide component in the organic polymer layer may be varied. In this way, layers of greater or lesser hardness can be deposited that are characterized by both good abrasion resistance and good barrier and corrosion-protective properties. But a disadvantage of this method is that true-to-quality layers can be attained only at deposition rates of a few nanometers per second. Hence, this technique proves to be unsuitable for the economical coating of large areas.
It is known to apply a layer comprising an inorganic component and an organic component to a substrate for improving gas imperviousness, with the organic component being non-uniformly distributed in the layer in the monomer state (EP 0 470 777 A2). The disadvantage of this method is that the layer is too brittle for further processing, and the vapor-deposition rates attainable with this method are too low.
Also known is a method of ion-assisted vacuum coating, in which a plasma is used to generate ions. In this method, ions are accelerated toward the substrate through the application of alternatingly positive and negative voltage pulses, relative to the plasma, between the substrate and a coating source (DE 44 12 906 C1). A disadvantage is that the layers produced in this manner are too hard for subsequent processing of the coated substrate.
It is known to produce oxide-polymer dispersion layers through simultaneous evaporation of polymers and metals with two evaporation sources (U.S. Pat. No. 4,048,349). This method is very costly, however, and, in addition, a subsequent thermal treatment must be performed for oxidation.